Scanning device for carrying out a 3D scan of a dental model, sliding panel therefore, and method therefor

ABSTRACT

The invention relates to a scanning system for carrying out a 3D scan of a tooth model, comprising an imaging device and a positioning system in the form of a sliding panel which can be positioned and has first locking means. On the locking panel there are provided second locking means which interact with the first locking means such that the sliding panel can assume one of several specified positions relative to the locking panel and locks in the selected position. 
     The invention also relates to a sliding panel for scanning dental models which has means for mounting the dental model and stands on projections disposed on its underside. 
     The invention also relates to a method of producing a 3D scan of a tooth model by the following steps:
         creating a first image of said object to be scanned at a precisely defined locked position,   moving said sliding panel to at least one further precisely defined locked position and creating another image at each such position, and   creating a 3D data set by evaluating the images produced at said at least two different, precisely defined positions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a scanning device for carrying out threedimensional scanning of dental models, to a sliding panel therefor, andto a method therefor.

2. The Prior Art

The extraoral scanning of dental impressions or models made from dentalimpressions with stationary scanning devices is disclosed in the priorart. The object to be scanned is usually larger than the range of imagedetection of the image detecting unit. It is therefore necessary tocreate images of the object to be scanned in several segments and toreposition the image detecting unit relatively to the object to bescanned for each image.

A device for determining the shape of a duplicate that contains aclamping device, a sensor contrivance, and a data storage unit, and inwhich the clamping device and the sensor contrivance are movablerelatively to each other, is disclosed in EP 0 913 130 A1.

The individual images are joined together by means of softwarecorrelation. In this process, the software attempts to find the sameidentifying points in two different images and thereby establish aposition relationship between the images. Due to imaging properties andother software-related inaccuracies incurred during the softwarecorrelation, errors cannot, in practice, be avoided when joining twocorrelated images. In the worst case, these errors can summate when aseries of images are joined together.

Furthermore, the technical computation requirements for correlatingimages with unknown misalignment are very great, which results in a longprocessing time.

It is thus an object of the invention to provide a scanning device, aswell as a method of scanning dental models, that permits rapid and exactscanning of dental models and is in addition cheap to produce incomparison with prior art devices.

SUMMARY AND OBJECTS OF THE INVENTION

This object is achieved by a scanning device as defined in claim 1 andby a method of scanning dental models as defined in claim 15.Advantageous developments are described in the subclaims.

The scanning device of the invention for carrying out 3D scanning ofdental models consists of an imaging device and a positioning system, inwhich the positioning system contains a panel that is adjustable inrelation to the imaging device and on which the object to be scanned canbe fixed. The adjustable panel is slid along a base plate that isstationary relative to the imaging device. The panel is in the form of asliding panel and contains a first set of locking means. The base plateis in the form of a locking panel and has a second set of locking means,which interacts with the first set of locking means in such a mannerthat the sliding panel can assume a plurality of specific positionsrelative to the locking panel and can be locked in the selectedposition.

In a scanning device thus constructed, the adjustable panel can onlyassume exactly defined positions. There is thus a finite number ofdisplacement vectors between individual images, which reduces thecorrelation of the various images to a discrete number of correlationpossibilities. In this manner, the number of computations required issubstantially reduced. Furthermore, there is no longer any propagationof summed correlation errors. The scanning results are thus moreaccurate than when scanning according to the prior art.

The imaging device is advantageously in the form of an image detectingunit. It is then possible to make a three dimensional scan withoutresorting to mechanical probing methods.

It is particularly advantageous if the range of image detection of theimage detecting unit is smaller than the object to be scanned. Suchimage detecting units can be produced very economically, because theresolution of the image sensor and/or the size of the optics can be keptsmall, which allows for an economic construction using standardcomponents.

An additional particularly advantageous embodiment of the inventionrelates to the use of an oral scanning camera for detecting the image.Oral scanning cameras are known in the prior art and, becauseconventional parts may be used and the design costs are less, a scanningdevice using an oral scanning camera can be sold cheaper than a scanningdevice incorporating a custom designed image detection device.

The scanning device is advantageously equipped with a light filter thatscreens the window through which light passes in and out, from theambient light. Ambient light reduces the quality of the images andconsequently the quality of the scan data. The light filter can beattached such that it also protects the lens of the scanning device frommechanical damage. This is accomplished by attaching the light filter infront of the lens.

The scanning device, in particular an oral scanning camera, operatesadvantageously with a telecentric optical path. A telecentric opticalpath has the advantage that the image of the object is always the samesize regardless of the distance of the object from the lens. Thisproperty makes it easier to analyze a telecentric image.

Advantageously, the distance from the image detecting unit from thesliding panel is adjustable. The depth of focus of all optical imagingsystems is limited by physical laws. Since not all objects to be scannedare in practice of the same height, it may be necessary to adjust theimage detecting device such that the sharp layer lies on the surface ofthe object to be scanned.

Advantageously, means are provided for measuring the distance of theimage detecting unit from the locking panel. Even with telecentric beampaths it may be necessary in some cases to know the relative distancefrom the image detecting unit to the object to be scanned, for example,in order to correlate successive images that were created at differentcamera heights.

The spacing between the locked positions in directions X and Y areadvantageously selected so that it is smaller than, or the same as, therange of image detection of the image detecting device and larger thanhalf of the range of image detection in the respective direction. Thespacing should be selected such that there is seamless joining oroverlapping of images created at adjacent locked positions, so that theimages can be joined together with no gaps and that the overlap zone issmall enough to ensure efficient scanning of the area being scannedinvolving as few images as possible.

It is particularly advantageous if the intervals between the lockedpositions in the X and Y directions are selected so that the image zonesscanned in adjacent positions overlap by at least one tenth of the rangeof image detection. This degree of overlap is sufficient to identifyidentical areas in adjacent images and thus ensure correlation.

One of the locking means is advantageously in the form of a projectionand the other locking means is advantageously in the form of adepression. Such locking means can be produced by simple productiontechniques but still exhibit a high degree of precision.

Either the sliding panel or the locking panel is advantageously equippedwith three projections. A three point means of support ensures a steadyand firm table-top for the sliding panel.

The projections advantageously have substantially convex bearingsurfaces. Such projections are resistant to deformations and usuallyhave a point of support that can be defined exactly.

The depressions are advantageously in the form of grooves. The slidingpanel can then be slid easily in one direction, because at least one ofthe projections slides in one of the grooves as the sliding panel isslid.

The land between two grooves is advantageously convex. This makes italmost impossible, in practice, to position the sliding panelincorrectly, as gravity causes the projection to slip automatically intothe groove.

It has been found to be particularly advantageous if the second lockingmeans are divided into a first area containing parallel, equidistantlyspaced grooves and a second area containing parallel, equidistantlyspaced grooves, and the grooves of the first area are substantially atright angles to the grooves of the second area. As a result, the slidingpanel can only be slid in the X and Y directions. Furthermore, it isparticularly easy to manufacture such an interlocking system.

The sliding panel is advantageously equipped with a device for adjustingthe angle of the object to be scanned.

Sometimes it is necessary not only to scan objects from a specificdirection but also to move the object into a different position relativeto the image detecting unit, as some objects have undercuts that cannotbe scanned in any other way.

The sliding panel is advantageously provided with marks, and theposition of said marks corresponds to the position of the first lockingmeans on the underside of the panel. The operator of the scanning systemcan thus easily check the position of the first locking means on thelocking panel.

It is particularly advantageous if the locking panel has at least onethrough hole for securing an object to be scanned, which will be heldimmobile and scanned in the X and Y directions, and the planar extent ofthe object to be scanned is smaller than the range of image detection ofthe image detecting unit. The object is secured by fastening means, andthe fastening means and the through hole are aligned so that the objectlies in the same range of image detection as the object to be scannedthat is positionable with the sliding panel. The object can also bealigned at an angle, for which a second through hole can be provided toensure that the object still lies in the range of image detection inspite of being positioned at an angle.

The scanning device is advantageously equipped with an evaluation unitthat computes a 3D data set based on the image data. A 3D data set canthus be generated immediately after scanning.

The distance between the locked positions of the sliding panel on thelocking panel can be advantageously stored in the evaluation unit andthe evaluation unit computes the 3D data set based on the scan data andsaid known distance.

The scanning device is advantageously calibrated by using a calibrationbody of known geometry, and the calibration data are stored in memory inthe evaluation unit and used to analyze the images. The scanning deviceconsists of a plurality of parts, the exact assemblage of which relativeto each other may vary from device to device due to manufacturingtolerances. Calibration is therefore advantageous to ensure the accuracyof the analysis.

The alignment of the image detecting unit relative to the directions ofdisplacement of the sliding panel is advantageously determined duringcalibration. Possibly, the displacement directions and the long sides ofthe image detector in the image detecting unit will not be exactlyparallel. A movement of the sliding panel will then be recorded as anangular displacement, which will be allowed for during correlation ofadjacent images by reference to the calibration data.

The spatial alignment of the locking panel relative to the imagedetecting unit is advantageously determined during calibration. If theplanes of the locking panel and the imaging detector in the imagedetecting unit are not absolutely parallel, a movement of the slidingpanel on the locking panel will also change the distance between theobject to be scanned and the image detecting unit.

The change of the range of image detection when changing the height ofthe image detecting unit above the locking panel is advantageouslydetermined during calibration. The optical path of the image detectingunit of an oral scanning camera is not necessarily perpendicular to thedirection of displacement of the image detecting unit when there is achange in the height of the image detecting device. In this way,different image segments will be imaged at different heights.

Advantageously, there are means on the locking panel for determining theposition of the sliding panel. This facilitates the automaticassociation of images which have been created at different positions ofthe sliding panel.

The surface of the sliding panel and/or the locking panel isadvantageously provided with a layer having good sliding properties.This makes it more difficult to position the sliding panel incorrectly,and, in addition, operation thereof is easier. In addition, the layercan be scratch proof in order to ensure a long useful life.

It is particularly advantageous if the scanning device is equipped witha display device on which the images generated by the image detectingunit can be displayed. The display device can then continuously displaythe current portion of the image in the image detecting device and theuser can then position the object to be scanned as desired and adjustthe sharp layer of the image detecting unit prior to image creation.

The locking panel used is advantageously replaceable. It is thenpossible to replace a damaged locking panel or install an improvedlocking panel, if available.

An additional object of the invention relates to a sliding panel for usein a dental scanning device in which the upper surface of the slidingpanel has a fastening means for a dental model and in which the bottomsurface of the sliding panel has projections on which the sliding panelrests. Such a sliding panel can be freely positioned within the limitsimposed by the dental scanning device. The sliding panel can be removedfrom the scanning system and a dental model can be fixed thereon. Suchfastening away from the image detecting unit is easier to accomplish.

The fastening means is advantageously rotatable and tiltable. Thisallows for a wider working zone, as a dental model to be scanned canthen be scanned from different directions and undercuts can be avoided.

Marks corresponding to the position of the projections on the undersideof the sliding panel are advantageously provided on the upper surface ofthe sliding panel. The user can then easily check the position of thepoints of support.

Advantageously there are three projections, of which two are alignedparallel to one edge of the sliding panel. This results in apreferential direction of displacement parallel to the edge of thesliding panel.

An additional object of the invention relates to a method for carryingout a 3D scan of dental models. A first image of the object to bescanned is produced, for which purpose the sliding panel is placed in afirst position as set by the locking means. Then an additional image isproduced in at least one more position as set by the locking means. Thisstep can be repeated as often as necessary until the object is scannedin its entirety. Finally, a 3D data set is computed by analyzing thepositions from the at least two different images from the preceding stepand accounting for the positions set by the locking means. Theproduction of a 3D scan of dental models by this procedure is veryreliable and the risk of errors is negligible.

The scanned image segment is advantageously checked by a user on adisplay device prior to the creation of each image and the height of theimaging unit is adjusted so as to position the sharp layer such that theregion to be imaged yields a sharp image. This ensures a sharply focusedimage of all scan-relevant data and thus a high degree of accuracy.

The imaging unit is advantageously equipped with means for determiningthe sharp image area and means for adjusting the sharp image area, bywhich means the imaging unit will automatically adjust the sharp imagearea. This ensures that the optimum sharp image area is set each timeand prevents incorrect operation.

The spacing between the locked positions of the sliding panel isadvantageously programmed into the evaluation unit and the images arejoined together by the evaluation unit with an offset specified by saidspacing between the locked positions of the sliding panel. With such aprocedure it is no longer necessary to correlate adjacent images, sothat no propagation of errors occurs. The assembled scan data are thusmore exact than independently correlated images.

The evaluation unit advantageously compares the individual images witheach other in a marginal region in order to determine the relativepositions of the images. In this manner the evaluation unit canautomatically recognize adjacently positioned images and join themtogether correctly.

A calibration of the scanning device is advantageously performed byscanning a calibration body on a sliding panel in several positionsthereof and allowing the evaluation unit to analyze the images at saidpositions and compute calibration data therefrom and store the same inmemory. This ensures an optimum of scanning accuracy in spite ofmanufacturing tolerances.

An offset of the image segment resulting from a height adjustment of theimage detecting unit is advantageously automatically corrected by theevaluation unit. To do this, the evaluation unit implements thedirection of displacement which was determined during calibration of thescanning device and which indicates the offset of two images created atdifferent heights which is required in order to move the same imagesegments of two images scanned in adjacent positions along the directionof displacement so that the two images match each other in the marginalregion as far as possible. This also compensates for any possiblevertical offset of the images relative to each other as a result ofimaging at different heights.

The single images are advantageously combined in a composite data set.The result is then a data set containing all relevant information andoptimally suitable for further processing.

BRIEF DESCRIPTION OF THE DRAWINGS

A scanning device of the invention is explained below with reference tothe drawings, in which:

FIG. 1 is a diagrammatic representation of a three dimensional scanningdevice of the invention,

FIG. 2 is a top view of a sliding panel with a tiltable fixing elementand the associated locking panel,

FIG. 3 is a top view of the sliding panel and the associated lockingpanel,

FIG. 4 is a perspective view of the underside of the sliding panel,

FIG. 5 is a perspective view of the locking panel without the slidingpanel,

FIG. 6 illustrates the rotary scanning of objects in the scanningdevice,

FIG. 7 shows the locking panel and a sliding panel for calibrating thesystem,

FIG. 8 shows the degrees of freedom of the scanning device which are tobe calibrated,

FIG. 9 illustrates the scanning zones with reference to a dental model,and

FIG. 10 illustrates the scanning method in the form of a programstructure diagram.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT OF THE INVENTION

FIG. 1 is a diagrammatic representation of a scanning device 1 of theinvention. The scanning system 1 comprises a locking panel 2, the designof which will be explained in more detail with reference to FIGS. 2 and3. On the locking panel 2 there is a sliding panel 3 that rests on thelocking panel 2 on the projections 4.1, 4.2, 4.3 (not shown). Theprojections 4.1 and 4.3 slide in the X direction in one of the grooves5.1, 5.2, 5.3, while the projection 4.2 slides in the Y direction in oneof the grooves 6.1, 6.2, 6.3. Engagement of the projections 4.1 and 4.3in the groove 5.2 and that of the projection 4.2 in the groove 6.1 isillustrated here. The locking panel 2 is provided with a scratch-proofcoating having good sliding properties.

On the locking panel 2 there is additionally provided a column 7, theheight of which is adjustable, with a mount 8 for a scanning camera 9which is in principle an oral scanning camera. The lens of the scanningcamera 9 is fitted with a light filter 10 to shield the optics of thescanning camera from the ambient illumination. The light filter 10 alsoprotects the exposed lens from physical damage. The scanning camera 9points to the sliding panel 3 to which the object 11 to be scanned isfixed, and the optical path 10′ is telecentric and is verticallyinclined at a slight angle of up to 5 degrees, as is customary forstandard oral scanning cameras.

The scanning camera 9 is connected to an evaluation unit 12 thatreceives, stores, and analyzes the scan data transmitted by the scanningcamera.

FIG. 2 clarifies the construction details of the locking panel 2 and thesliding panel 3. On the locking panel 2 there are two groups each ofparallel equidistant grooves 5.1, 5.2, 5.3 and 6.1, 6.2, 6.3 and the twogroups are substantially at right angles to each other. The landsseparating the grooves, for example that between 5.1 and 5.2, designatedin the figure as 13.1, are substantially convex. The locking panel 2 canbe fixed to a table by way of the drill holes 14.1, 14.2, 14.3. Theintervals ΔX between the grooves in the X direction 6.1, 6.2, 6.3 and ΔYbetween the grooves in the Y direction 5.1, 5.2, 5.3 match the range ofimage detection of the scanning camera 9. In this case the imagedetected is 17 mm long in the X direction and 14 mm wide in the Ydirection. A 2 mm overlap for each marginal region is taken intoaccount, so that ΔX in this case equals 15 mm and ΔY equals 12 mm.

A swivel-type mount 15 is attached to the sliding panel 3 which makes itpossible to position an object 11 fixed thereto for scanning at anydesired height, direction and angle.

Additionally, there are marks 16.1, 16.2, 16.3 on the top surface of thesliding panel 3 that correspond to the position of the points of support4.1, 4.2, 4.3 (not shown) underneath.

A top view of the locking panel 2 and the sliding panel 3 is illustratedin FIG. 3. Here the projections 4.1 and 4.3 are in groove 5.2, and theprojection 4.2 is in groove 6.2. Following creation of an image, thesliding panel 3 can now be slid from this first position to anotherprecisely defined position, for example in the Y direction by moving theprojections 4.1 and 4.3 to the groove 5.1. During this movement,projection 4.2 remains in groove 6.2. Movement in the X direction isalso possible, in which case the projections 4.1 and 4.3 will slidealong the groove 5.2 while the projection 4.2 is moved to groove 6.3.

Taking all possible positions of the sliding panel into account, thereresults a matrix showing equal intervals in the X and the Y directions.

There is a drill hole 16 in the locking panel 2 of the sliding panel formounting a holder. Underneath the locking panel there is provided arotatable, upwardly inclined holder for holding an object that can bescanned in its entirety and from all sides by the scanning camera 9.

In FIG. 4, the sliding panel 3 is illustrated as viewed from itsunderside. The projections 4.1, 4.2, and 4.3 are spherical in shape.This, in conjunction with the convex ridges between the grooves, makesincorrect positioning almost impossible.

FIG. 5 is a perspective view of the locking panel of the invention.There are two through holes 16, 17 in the locking panel. These throughholes 16, 17 are for the insertion of a holder on which the dental model18 to be scanned can be mounted. The through holes are arranged suchthat the tooth can be positioned in the same optical path of the imagedetecting device through either hole by selecting a holder designed tofit properly. The through holes 16, 17 are located on the ridge betweenthe grooves 6.3 and 6.4, making it impossible to slide the projection4.2 into one of the through holes 16, 17 and thus to position thesliding panel incorrectly.

The through hole 16 serves to hold a tooth at a specified angle α, whichis in this case 30° (FIG. 6). The holder is rotatable so that the toothcan be scanned from all sides. The through hole allows the tooth to bealigned exactly perpendicular to the surface of the locking panel 2 sothat scanning of any cavities on the upper surface of the dental model18 is possible.

The function of the through hole 16, 17 and the positioning of theobjects to be scanned by rotary scanning are illustrated in FIG. 6. Anobject 19 is fastened to a holder 20 which is pressed onto the spindle21 of a motor 22 located underneath the locking panel 2. The object tobe scanned, for example a tooth, is located in the optical path 10′ ofthe image detecting system 9. The tooth 19 is turned progressively bythe motor 22 through a specific angle of, say, 45° per step, after whichan additional image is created. The angle of 30° ensures that the tooth19 is scanned completely from all sides without any undercuts. If thereare cavities on the upper surface of the tooth 19, the holder can bepressed onto the spindle 23 on the motor 24 through the through hole 17.In this manner, images of the upper surface having such cavities of thetooth 19 can be created from different directions.

FIG. 7 shows a calibration system 25 having a calibration body 26 forcalibrating the scanning device. For this purpose the calibration system25, like the sliding panel, has three projections (not shown) thatengage in the grooves 5.1, 5.2, 5.3 and 6.1, 6.2, 6.3 on the lockingpanel 2. The calibration body 26 is a cylinder made to a very highdegree of precision and firmly attached to the calibration unit 25. Theevaluation unit 12 is able to detect the axis of the calibration body 26from the scan data.

The calibration procedure is explained below with reference to FIG. 8and FIG. 9. The locking panel 2 of the three dimensional scanning device1 has an alignment specified by the spatial coordinates designatedX_(R), Y_(R) and Z_(R). These coordinates are chosen so that X_(R)indicates the direction of one displacement vector and Y_(R) indicatesthe direction of the other displacement vector, while Z_(R) indicatesthe direction of the perpendicular to the surface of the locking panel2. Furthermore there is an additional coordinate system X_(S), Y_(S),Z_(S) for the sensor 27, which is skewed relative to the coordinatesystem of the locking panel 2. The directions X_(S) and Y_(S) areparallel to the edges of the image sensor. The direction Z_(S) definesthe vector of the perpendicular to the surface of the image sensor 27.The two sets of coordinates X_(R), Y_(R), Z_(R) and X_(S), Y_(S), Z_(S)are skewed and tilted relatively to each other as a result ofmanufacturing tolerances.

The first objective of the calibration procedure is to determine thepositions of the two coordinate systems relative to each other. This isaccomplished by scanning the calibration unit 25 illustrated in FIG. 7in four different positions representing the extreme positions of saidcalibration unit 25 on the locking panel 2. From the change in the axialposition of the axis of the calibration body 26, the evaluation unit candefine, on the one hand, the relative alignment of the two coordinatesystems to each other and, on the other hand, the displacement vectorsX_(R) and Y_(R) of the sliding panel 3 with respect to the position ofthe image sensor, given by X_(S) und Y_(S).

Finally an additional calibration is performed to determine the absoluteposition of the two coordinate systems to each other as a function ofthe height H of the image detecting unit from the locking panel. Thevector R(H), together with the image offset caused by the inclinedoptical path 10′, is responsible for the absolute image offset as afunction of the change in height.

In order to ascertain this relationship the calibration unit 25 isplaced in two positions perpendicular to each other on the locking panel2 and scanned at two heights in each position by the image detectingsystem 9. The displacement vector R(H) can be unambiguously determinedfrom the four images.

FIG. 9 illustrates scanning of a dental model 28. The dental model 28 ismoved together with the sliding panel 3 on the locking panel and canassume only specific positions represented here by P_(X1),P_(X2),P_(X3)and P_(Y1,) P_(Y2,) P_(Y3.) The intervals ΔX in the X direction and ΔYin the Y direction are defined by the distances between the grooves. Therange of image detection X_(S), Y_(S) of the sensor is larger than thelocking intervals. This results in overlap zones in adjacent images thatare illustrated here by hatching. These overlap zones are used by theevaluation unit 12 to join the corresponding single images together.

FIG. 10 illustrates the method of the invention with reference to a flowdiagram in a first position of the sliding panel for creating a firstimage. The image data are stored on a data medium located in theevaluation unit. Afterwards the sliding panel is moved along a groove inthe X or Y direction, as explained in the above description of thedrawings. Then a new image is created in this new position. The data areagain stored in the data storage device of the evaluation unit. Ifadditional images are to be made, the last step following movement ofthe sliding panel is repeated until the object to be scanned has beenscanned in its entirety. On completion of the scan, the evaluation unit12 retrieves the data from the data storage device, correlates theoverlap zones of the individual images and joins the images together,taking into account the known distance between the grooves 5.1, 5.2 and6.1, 6.2, and computes from all of the above a complete 3D data set.

LIST OF REFERENCE NUMERALS

-   1 scanning system-   2 locking panel-   3 sliding panel-   4.1, 4.2, 4.3 projections-   5.1, 5.2, 5.3 grooves in the X direction-   6.1, 6.2, 6.3 grooves in the Y direction-   7 column-   8 mount-   9 scanning camera-   10 lens protector-   10′ optical path-   11 object to be scanned-   12 evaluation unit-   13.1, 13.2, 13.3 ridge-   14.1, 14.2, 14.3 attachment bores-   15 rotatable mount-   16 through hole for rotary scanning-   16.1, 16.2, 16.3 mark-   17 through hole for vertical scanning-   18 holder-   19 tooth-   20 holder-   21 spindle-   22 motor-   23 spindle-   24 motor-   25 calibration device-   26 calibration body-   27 sensor-   28 dental model

1-32. (canceled)
 33. A method of producing a 3D scan of a tooth model,in which an object (11) to be scanned is fixed to a sliding panel (3)and said object (11) to be scanned is imaged by an image detecting unit(9) as a number of single images, and for the creation of a 3D data setof the tooth model (11) a computation is carried out by an evaluationunit (12), comprising the following steps: creating a first image ofsaid object (11) to be scanned at a specific locked position, movingsaid sliding panel (3) to at least one further specific locked positionand creating another image at each such position and creating a 3D dataset by evaluating the images produced at said at least two different,precisely defined positions.
 34. A method as defined in claim 33,wherein the image segment is viewed on a display by the operator priorto the creation of each new image and the sharp layer is positioned byadjusting the height of the image detecting unit (9) such that theregion to be imaged yields a sharp image.
 35. A method as defined inclaim 33, wherein the image detecting unit (9) automatically adjusts thesharp image area by implementing means for determining the sharp imagearea and means for adjusting the position of the sharp image area.
 36. Amethod as defined in claim 33, wherein the spacing of the lockedpositions of the sliding panel (2) are known to said evaluation unit(12) which joins the images together with an offset specified by saidspacing of the locked positions of the sliding panel (2).
 37. A methodas defined in claim 33, wherein the evaluation unit (12) compares theindividual images with each other in a marginal area of the images inorder to determine a position relationship between the images.
 38. Amethod as defined in claim 33, wherein a calibration of the scanningsystem (1) is carried out by creating images of a calibration body (26)in a plurality of positions on a sliding panel (25) and evaluating saidimages at said positions in said evaluation unit (12) and storing thecalibration data in memory.
 39. A method as defined in claim 33, whereina any displacement of the image segment occurring during verticaladjustment of the image detecting system (9) is automatically correctedby the evaluation unit (12) by implementing the direction ofdisplacement determined during calibration of the scanning system (1)for the purpose of shifting identical image segments in two imagescreated at adjacent positions along the direction of displacement suchthat the marginal areas of the two images match each other as far aspossible.
 40. A method as defined in claim 33, wherein the single imagesare combined to form a composite data set.